Apparatus fob and method of



Nov. 29, 1949 G. W. BORKLAND APPARATUS FOR AND METHOD OF FORMING SHEETMATERIAL Original Filed May 25, 1944 1;" I 5. 2 6-4. mi fu lzmyum\\ II!v fizveraor W 60M Reiaued Nov. 29, 1949 FFICE APPARATUS FOR AND METHODOF FORMING SHEET MATERIAL Gustave w. Borkland, Marion, Ind. Original No.2,442.338, dated June 1, 1948, Serial No. 537,353, May 25, 1944.Application for reissue October 4, 1949, Serial No. 119,431

8 Claims.

This invention relates to the forming of hollow I articles from sheetsor strips of plastic material and more particularly to the forming ofsuch articles from material of this kind by the use of mechanicalpressure and suction, the mechanical pressure being employed first in apreliminary partial forming oi-the article and the suction coming intoplay thereafter for the completion of the forming.

One of the objects of the invention is the provision of improvedapparatus for forming sheetlike plastic material comprising a singleforming punch, means for maintaining the sheet or strip material in apredetermined position during the forming operation, and suction meanscontributing to the forming operation.

Another object of my invention is to provide an improved method andapparatus for forming cupshaped articles of plastic material havingprotuberant zones interspaced with reentrant zones by the use'of asingle forming punch combinediy operating with air suction.

Inasmuch as it is dimcult to make perfectly mating male and female dies,especially where thin materials are to be formed, there is great dangerin forming thin materials, if perfect mating is not obtained, ofproducing an article of varying wall thickness, which, upon cooling ofthe article, or in its use, may result in cracking. Furthermore, themaking of both male and fee male dies is expensive. Therefore, a furtheraim is toprovide an apparatus and method for the purpose described whichwill eliminate the necessity of female dies and the consequent expensethereof.

Further objects and advantages of the invention will be apparent fromthe description and claims.

In the drawings, in which my invention is illustrated,

Figure 1 is an axial sectional view showing the forming punch inposition with respect to the sheet to be formed.

Fig. 2 is a view similar to Fig. 1 showing the position of the partsjust prior to the final phase of movement of the forming punch;

Fig. 3 is a fragmentary axial sectional view showing an intermediateposition of the forming punch; V

Fig. 4 is a cross-section on the line 4-4 of Fig. 2, and

Fig. 5 is a schematic representation of a continuousproduction systemembodying the invention. v

The article to be formed may be circular, rec-v tangular or otherwise inoutline, but by way of illustration the apparatus will be described asused for a circular molded article.

Referring now to the drawings in detail, there is shown a circularplaten member III supported in any suitable manner on the bed I I of amolding press of a common type (not shown) and provided with a spacingportion I2 to allow movement of the forming die therein. uBolts I3 maybeprovided to maintain the platen member ID in position on the bed I I, aflange ll being provided on member III for that purpose.

Extending around the periphery of member I0 is the flange I5 serving tosupport on its upper face I6 the lower of a pair of clamping members Hand I8, as shown, each consisting of a ring adapted to be maintained inclamping engagement with the blank by thumb screws, clamps, orequivalent readily detachable holding means.

The movable forming punch 2i comprises a shaping surface formed tocorrespond with the desired contour of the inner surface of the articleto be molded, which in the present case is illustrated as of generallycupped form having protuberant zones 22a, 22b and 220 interspersed withreentrant zones 23a and 231). At this juncture it will be understoodthat I.do notintend to limit the invention to the number of protuberantzones and re-entrant zones illustrated, but that they may be more orless in number depending upon the shape'of the article tobe formed. Atits upper end the forming punch 2| includes a chamber 24' of generallycylindricalshape, communicating with a source of vacuum (not shown)through a flexible tube 25. The upper portion 26 of the forming punch 2!receives the piston rod 21 of the press by means of which intermittentreciprocating motion is imparted to the forming punch.

Serving to connect chamber 24 with the reentrant zones 23a. and 23b is aplurality of passages, as shown, comprising two concentric groups ofapertures 3| and 32 (Fig. 4), although if preferred the passages,between chamber 24 and zones 23a and 23b may be annular and substantially continuous about the periphery, i. e., interrupted only by ribsto maintain the integral nature of forming punch 2 I Extending aroundthe 'peripheryof member ID is the inner flange 33, preferably rounded atits inner and upper corner 34 for a purpose to appear later. 1

Operation is as follows: .The sheet or blank of plastic material isplaced between clamping rings I1 and I8, as shown, to maintain theposition of u the blank during the forming and stripping operation. Ifthe nature of the material is such that ductility must be imparted byheating or otherwise, such part of the process may be performed prior toor after the time the blank is brought into position. Necessarily, theductilizing of the blank must be sufllcient to render the same formablebut not excessively to cause it to sag under gravity.

Following any desired ductilizing of the blank,

the forming punch 2i begins to move downward against the material, asshown in Fig. 3, and an air suction is applied through tube 25, achamber 24 and passages II and 32. Depending upon the particular finalshape of the article, the suction maybe applied continuously during theentire downward movement of the forming punch; during a portion of saidmovement to terminate at the same time as the forming punch reaches itslowest position, or it may be applied during a portion of the downwardmovement of the forming punch beginning after the forming punch beginsto move and terminating before the forming punch reaches its lowestposition. Any such timing of the application of suction with respect tothe cycle of movement of the forming punch may be by means of anautomatically or manually controlled valve 35 on the tube 25.

After the forming punch 2| has reached a position where, for example,the blank bridges protuberances 22a and 22b, the re-entrant zone 230.will be closed off from atmosphere and the suction will .draw thatbridging p rtion of sheet material snugly into the re-entran; position,as shown in Fig. 3. Upon further downward movement of the forming punch,the material will bridge; for example, between protuberances 22b and 220and the suction will draw that bridging portion of the material snuglyinto the re-entrant position shown in Fig. 2, thus completing theforming operation. Thereafter, the formed article, when it hasresolidified to a state where it may be safely handled, is severed fromthe unused portion of the blank by shearing portions of the formingpunch cooperating with flange 33 shown in one form in Fig. 5, or it maybe separated at a later stage.

Stripping of the formed article from the forming punch is preferablydone after the suction has been released, and may be accomplished bystripping means incorporated in the forming punch, e. g., plungers orstripping rings; or by applying air pressure through tube 25, chamber 24and apertures 3| and 32 to blow the article off the forming punch.

A continuous production arrangement is illustrated in Fig. 5 wherein theforming punch H is shifted by hand, or by any suitable means (notillustrated) from the forming position to a shearing position (showndotted) the plastic or similar material being fed from a reel 40 into apunch press 42, shown schematically, through some suitabel heating means4| where the plastic or similar material is heated to the proper ductilestate so that forming may take place without cracking. The punch press42 is shown as comprising members 44, 45, and 46 cooperating with theforming punch during the forming and shearing operations, and guidemeans in which the forming punch is arranged to be laterally shiftable,the guide means comprising suitable frame members 41, guide bars 46 and49 supported by said frame members 41, and a guide block 50 movablebetween the guide bars through which the piston rod 21 is arranged tomove. It will be understood that the guide frame comprising members 41,48, and 49 is stationary and that the forming punch is moved within theguide frame byhand or by any suitable means. The forming punch holder 52to which rod 21 is fastened is provided with two ring flanges 53 and 54,the ring flange 53 acting as one bearing surface for springs 55, theother ends of which bear against aninwardly directed ring flange 56forming part of a circular clamping and stripping ring 51 and overlyingthe ring flange 54, the ring flange 56 being forced against the ringflange 54 by springs 55. The forming punch holder 52 is provided with asuction chamber and means for producing suction therein in a mannersimilar to that illustrated in Figs. 1 and 3, such suction means beingmanually or automatically operable in proper sequence. When the formingpunch is forced downwardly, the lower edge 60 of the clamping ring 51holds the plastic material firmly against the members 44 and 45 afterwhich continued downward movement of the forming punch brings theforming punch into contact with the plastic material and deforms it intoa cupped structure with the cooperation of suitable suction as describedin connection with Fig. 2.' After completing the formation of the cuppedstructure, the forming punch 2| is retracted, the sheet of plastic beingcarried along with the die since no shearing of the cupped formation hasoccurred and the suction is maintained during the retraction, the

springs 55 not being of suflicient strength to force the sheet ofplastic material away from the forming punch against the suction force.After the forming punch has been completely retracted, suitable meansare brought into operation to shift the forming punch laterally in theguide bars 48 and 49 to the shearing position shown dotted in Fig. 5,carrying the cupped formation along with it and thus feeding the plasticsheet into the press. In the shifted position the forming punch againmoves downward and during this movement the edge 6| of the flange ring54 cooperates with the edges 62 and 63 of members 45 and 46,respectively, to shear the cup from the plastic strip as the loweroutside edge 6| of the ring 54 passes the edges 62 and 63, Whilecompressed air is supplied through the suction pipe 25 to eject or blowoff the completed cup, following which the forming punch is againretracted, dur- -ing which movement the clamping ring 51 prevents theremainder of the plastic strip from moving with the forming punch. Afterretraction following the shearing movement, the forming punch is movedto its initial position to begin a new series of operations.

In practice, I have found that material varying in thickness from 0.002inch to .500 inch may be formed by the apparatus and method described,and by using a vacuum ranging from five inches to twenty-nine inches ofmercury. Ductilizing temperature or other ductilizing treatment woulddepend upon the thickness of the material, its chemical nature and theshape of the article to be formed.

Any suitable material may be used for the ductile sheet, such ascellulose acetate, ethyl cellulose, and various other plastics, or thelike.

Further modifications will be apparent to those skilled in the art, andit is desired, therefore, thatthe invention be limited only by the scopeof the appended claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A method of forming a ductile sheet of ma- -terial into a formincluding protuberances interspaced with indentations which comprisesanchoring said sheet during the forming operation at an unformed portionthereof, effecting relative movement between said anchored sheet and aforming punch having corresponding protuberances and indentationsthereagainst until at least part'of the material is bridging a pair ofprotuberances to form a closed chamber between said protuberances andtheface of the forming punch, and then applying suction to the chamber tosuck said bridging portion of the material against the face of theforming punch, then continuing the movement of the forming punch tocause another part of the material to bridge a pair of protuberances toform another closed chamber as aforesaid and applying suction to thechamber as aforesaid.

2. A method of forming a ductile sheet of material into a form includingprotuberances interspaced with indentations which comprises anchoringsaid sheet during the forming operation at an unformed portion thereof,effecting relative movement between said anchored sheet and a formingpunch having corresponding protuberances and indentations thereagainstto cause the protuberances to engage the sheet and cause the sheet tobridge over the indentations, and at a predetermined time in the cycleof movement of said forming punch applying suction between theworking'surface of said forming punch and said sheet in zones whereinsaid indentations in said sheet are desired.

3. Apparatus for forming a ductile sheet of plastic material into acupped formation comprising supporting means for holding the portion ofthe sheet adjacent the portion to be cupped against lateral slipping, areciprocable forming punch movable transversely against a portion of thesheet to be cupped, means associated with said forming punch forapplying suction to the cupped portion of the sheet during the formingpunch applying and withdrawing movement while the sheet is still held bysaid holding means to suck the sheet against the forming punch surfaceduring the forming movement and to hold it against the forming punchduring the withdrawing movement and guide means for mounting saidforming punch for lateral shifting movement with respect to saidsupporting means.

4. In the art of successively forming articles from thermoplastic sheetmaterial by the use of forming means having a forming surface directlyengageable with the sheet material, a method of forming a ductilesheetof material into a form including protuberances interspaced withindentations which comprises anchoring said sheet during the formingoperation at an unformed portion thereof, effecting relative movementbetween said anchored sheet and a forming punch having correspondingprotuberances and indentations thereagainst until at least part of thematerial is bridging a pair of protuberances to form a closed chamberbetween said protuberances and the face of the forming punch, then'engageable with the sheet material, a method of forming a ductile sheetof material into a form including protuberances interspaced withindentations which comprises anchoring said sheet during the formingoperation at an unformed portion thereof, heating the sheet to aductilizing temperature, effecting relativemovement between saidanchored sheet and a forming punch having corresponding protuberancesand indentations thereagainst until at least part of the material isbridging a pair of protuberances to form a closed chamber-between saidprotuberances and the face of the forming punch, then applying suctionto the chamber to suck said,

bridging portion of the material against the face of the forming punch,and effecting the separation of the formed sheet from the face of theforming punch, said sheet material after heating being moved in heatedductile condition into position for co-operation with said formingpunch.

6. In the art of successively forming articles from thermoplastic sheetmaterial by the use of forming means having a forming surface directlyengageahle with the sheet material, a method for forming a ductile sheetof plastic material into a cupped formation having spaced protuberantsurfaces and a re-entrant surface between said protuberant surfacescomprising holding the portion of the sheet around the portion to becupped against lateral slipping, effecting relative movement betweensaid held sheet and forming means having protuberant surfaces forforming the protuberant surfaces in a cupped formation, and a re-entrantsurface between said protuberant surfaces, transversely against saidsheet to form the protuberant surfaces on the sheet and cause the sheetto bridge over the reentrant surface, exhausting the air from the spacebetween the re-entrant surface and the sheet to cause the sheet to beforced against the re-entrant surface, and effecting separation of theformed ?heet from said protuberant and re-entrant suraces.

7. In the art of successively forming articles from thermoplastic sheetmaterial by the use of forming means having a-forming surface directlyengageable with the sheet material, a method for forming a ductile sheetof plastic material into a cupped formation having spaced protuberantsurfaces and a re-entrant surface between said protuberant surfacescomprising heating the sheet to a ductilizing temperature, holding theportion of the sheet around the portion to be cupped against lateralslipping, effecting relative movement between said held sheet andforming means having protuberant surfaces for forming the protuberantsurfaces in a cupped formation, and reentrant surface between saidprotuberant surfaces, transversely against said sheet to form theprotuberant surfaces on the sheet and cause the sheet to bridge over there-entrant surface, exhausting the air from the space between thereentrant surface and the sheet to cause the sheet to be forced againstthe re-entrant surface, and effecting separation of the formed sheetfrom said protuberant and re-entrant surfaces, said sheet material afterheating being moved in heated ductile condition into position forco-operation with said forming means 8. In the art of successivelyforming articles from thermoplastic sheet. material by the use offorming means having a forming surface directly engageable with thesheet material, a method for forming a ductile sheet of plastic materialinto a cupped formation having spaced protuberant surfaces and are-entrant surface between said protuberant surfaces comprising heatingthe sheet to a ductiliz'ing temperature, holding the portion of thesheet around the portion to be cupped against lateral slipping,effecting relative movement between said held sheet and forming meanshaving protuberant surfaces for forming the protuberant surfaces in acupped formation, and a re-entrant surface between said protuberantsurfaces, transversely against said sheet to form the protuberantsurfaces on the sheet and cause the sheet to bridge over the re-entrantsurface to 1 form a chamber closed except for the exhaust of airtherefrom, exhausting the air from the space between there-entrantsurface and the'sheet to cause the sheet to be forced againstthe re-entrant surface, and efiecting separation of the formed sheetfrom said protuberant and re-entrant surfaces, said sheet material afterheating being moved in heated ductile condition into position forco-operation with said forming means.

- GUSTAVE W. BORKLAND.

No references cited.

